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TodoContract.sol

pragma solidity >=0.4.22 <0.6.0;
contract SimpleContract {
    
    struct TodoItem {
        uint256 id;
        string name;
        bool completed;
    }

    struct User {
        string name;
        TodoItem[] todos;
    }
  
    address owner;
    mapping(address => User) users;

    constructor() public {
        owner = msg.sender;
    }
    
    function addTodo(address _toUser, string memory _name) public {
        uint256 arraySize = users[_toUser].todos.length;
        users[_toUser].todos.push(TodoItem({id: arraySize, name: _name, completed: false}));
    }
    
    function getTodoLength(address _byUser) public view returns (uint256) {
        return users[_byUser].todos.length;   
    }
    
    function getTodoItem(address _byUser, uint _todoId) public view returns (uint, string memory, bool) {
        require(users[_byUser].todos.length > _todoId, "Bad Id inseted");
        TodoItem memory todo = users[_byUser].todos[_todoId];
       return (todo.id, todo.name, todo.completed);  
    }
    
    function toggleTodo(address _byUser, uint _todoId, bool _completed) public {
        require(msg.sender == owner || msg.sender == _byUser, 
        "Only owner or assigned user can change task to completed");
        users[_byUser].todos[_todoId].completed = _completed;
    }
        
}